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\begin{equation*}\frac{\Delta^2F(P_0)}{\Delta_1P^2}=\frac{\Delta F'(P_0)}{\Delta_1P}=\frac{\frac{\Delta F(P_1)}{\Delta_1P}-\frac{\Delta F(P_0)}{\Delta_1P}}{\Delta_1P},\,\!\end{equation*}
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